Semiconductor device with nanowire plugs and method for fabricating the same

ABSTRACT

The present application discloses a semiconductor device and a method for fabricating the semiconductor device. The semiconductor device includes a substrate having first regions and second regions; a plurality of bit line contacts and a plurality of capacitor contacts disposed over the plurality of first regions and second regions; a landing pad disposed over one of the plurality of capacitor contacts, the landing pad comprising a protruding portion of a capacitor plug and a first spacer disposed on a sidewall of the protruding portion; a conductive plug disposed over the landing pad; and a plurality of bit lines disposed over the plurality of bit line contacts; and a capacitor structure disposed over the conductive plug. The capacitor plug includes a plurality of nanowires, a conductive liner disposed over the plurality of nanowires, and a conductor disposed over the conductive liner.

TECHNICAL FIELD

The present disclosure relates to a semiconductor device and a methodfor fabricating the semiconductor device, and more particularly, to asemiconductor device with a nanowire plug and a method for fabricatingthe semiconductor device with coverage layer.

DISCUSSION OF THE BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment. The dimensions of semiconductor devices arecontinuously being scaled down to meet the increasing demand ofcomputing ability. However, a variety of issues arise during thescaling-down process and impact the final electrical characteristics,quality, and yield. Therefore, challenges remain in achieving improvedperformance, quality, yield, and reliability.

This Discussion of the Background section is provided for backgroundinformation only. The statements in this Discussion of the Backgroundare not an admission that the subject matter disclosed in this sectionconstitutes prior art to the present disclosure, and no part of thisDiscussion of the Background section may be used as an admission thatany part of this application, including this Discussion of theBackground section, constitutes prior art to the present disclosure.

SUMMARY

One aspect of the present disclosure provides a semiconductor device,comprising: a substrate having a plurality of first regions and secondregions; a plurality of bit line contacts and a plurality of capacitorcontacts disposed respectively over the plurality of first regions andsecond regions; a landing pad disposed over one of the plurality ofcapacitor contacts, the landing pad comprising a protruding portion of acapacitor plug and a first spacer disposed on a sidewall of theprotruding portion; a conductive plug disposed over the landing pad,wherein the capacitor plug comprises a plurality of nanowires, aconductive liner disposed over the plurality of nanowires, and aconductor disposed over the conductive liner; a plurality of bit linesdisposed respectively over the plurality of bit line contacts; and acapacitor structure disposed over the conductive plug.

In some embodiments, the first spacer comprises metal silicide, and awidth of the first spacer is larger than a width of the capacitor plug.

In some embodiments, at least one of the plurality of bit lines is awavy line extending between two adjacent capacitor contacts.

In some embodiments, the semiconductor device further comprises a secondspacer disposed over the first spacer, wherein the first spacercomprises polysilicon.

In some embodiments, the second spacer comprises metal silicide.

In some embodiments, at least one of the plurality of capacitor contactshaving a neck portion and a head portion over the neck portion.

In some embodiments, the upper width of the head portion is larger thana bottom width of the head portion, and the head portion has a curvedsidewall.

In some embodiments, the upper width of the neck portion issubstantially the same as a bottom width of the head portion.

In some embodiments, the head portion has tapered profile.

In some embodiments, an upper width of the head portion is larger thanan upper width of the neck portion.

Another aspect of the present disclosure provides a method forfabricating a semiconductor device, comprising: providing a substrateincluding a plurality of first regions and second regions; forming aplurality of bit line contacts respectively over the plurality of firstregions; forming a plurality of bit lines respectively over theplurality of bit line contacts; forming a plurality of capacitorcontacts respectively over the plurality of second regions; forming alanding pad over one of the plurality of capacitor contacts, wherein thelanding pad comprises a protruding portion of a capacitor plug and afirst spacer on a sidewall of the protruding portion; forming aconductive plug over the landing pad, wherein the capacitor plugcomprises a plurality of nanowires, a conductive liner over theplurality of nanowires, and a conductor over the conductive liner; andforming a capacitor structure over the conductive plug; wherein at leastone of the plurality of bit lines is a wavy line extending between twoadjacent capacitor contacts.

In some embodiments, forming a conductive plug comprises: forming aplurality of catalyst dots over the landing pad; forming the pluralityof nanowires from the plurality of catalyst dots; depositing a silicidelayer and a conductor over the plurality of nanowires; and planarizingthe plurality of nanowires to trim the plurality of nanowires to be ofsame length.

In some embodiments, the first spacer comprises metal silicide.

In some embodiments, the method for fabricating the semiconductor devicefurther comprises: forming a plurality of second spacers respectivelyover the plurality of first spacers, wherein the first spacer comprisespolysilicon.

In some embodiments, the second spacer comprises metal silicide.

In some embodiments, at least one of the plurality of capacitor contactshaving a neck portion and a head portion over the neck portion, whereinan upper width of the head portion is larger than an upper width of theneck portion.

In some embodiments, forming a plurality of capacitor contacts comprise:forming a contact hole in a dielectric stack having a first layer and asecond layer over the first layer; removing a portion of the secondlayer around the contact hole to form a transformed hole having a narrowportion in the first layer and a wide portion in the second layer; andfilling a conductive material into the transformed hole.

In some embodiments, the contact hole is formed integrally with a bitline trench in the second layer.

In some embodiments, the method for fabricating the semiconductor devicefurther comprises: filling the bit line trench and a lower portion ofthe contact hole with a filling material.

In some embodiments, a width of the first spacer is larger than a widthof the capacitor plug.

High aspect ratio conductive plug is implemented by the nanowires toelectrically connect the source/drain regions in the substrate and thecapacitor structures over the source/drain regions.

Furthermore, the landing pad has the first spacer, wherein a width ofthe first spacer is larger than a width of the capacitor plug, themisalignment between the subsequently formed capacitor structure and thelanding pad can be dramatically solved, wherein a width of the firstspacer is larger than a width of the capacitor plug.

In addition, due to the capacitor contact having the neck portion andthe head portion with a tapered profile, the misalignment between thesubsequently formed capacitor structure and the capacitor contact can bedramatically solved. In addition, the coverage layer may reduceformation of defects in the semiconductor device; therefore, the yieldof the semiconductor device increases correspondingly.

The foregoing has outlined rather broadly the features and technicaladvantages of the present disclosure in order that the detaileddescription of the disclosure that follows may be better understood.Additional features and advantages of the disclosure will be describedhereinafter, and form the subject of the claims of the disclosure. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures or processes for carrying outthe same purposes of the present disclosure. It should also be realizedby those skilled in the art that such equivalent constructions do notdepart from the spirit and scope of the disclosure as set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates, in a flowchart diagram form, a method forfabricating a semiconductor device in accordance with one embodiment ofthe present disclosure.

FIGS. 2 and 3 illustrate, in schematic cross-sectional diagrams, part ofa flow of fabricating a semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 4 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 3.

FIGS. 5 to 7 illustrate, in schematic cross-sectional diagrams, part ofthe flow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 8 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 7.

FIG. 9 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 10 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 11 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 10.

FIG. 12 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 13 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 12.

FIG. 14 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 15 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 14.

FIG. 16 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 17 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 16.

FIG. 18 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 19 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 18.

FIG. 20 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

FIG. 21 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 20.

FIGS. 22 to 26 illustrate, in schematic cross-sectional diagrams, partof the flow of fabricating the semiconductor device in accordance withone embodiment of the present disclosure.

FIGS. 27 to 33 illustrates, in a close-up schematic cross-sectionaldiagram, part of the flow of fabricating the conductive plug inaccordance with one embodiment of the present disclosure.

FIGS. 34 to 36 illustrate, in schematic cross-sectional diagrams, partof the flow of fabricating the semiconductor device in accordance withone embodiment of the present disclosure.

FIG. 37 illustrates, in a schematic top-view diagram, the semiconductordevice in accordance with FIG. 36.

FIGS. 38 to 41 illustrate, in schematic cross-sectional diagrams, partof the flow of fabricating the semiconductor device in accordance withone embodiment of the present disclosure.

FIGS. 42 to 43 illustrate, in schematic cross-sectional view diagrams,some semiconductor devices in accordance with some embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

It will be understood that when an element or layer is referred to asbeing “connected to,” or “coupled to” another element or layer, it canbe directly connected to or coupled to another element or layer orintervening elements or layers may be present.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. Unless indicated otherwise, these terms areonly used to distinguish one element from another element. Thus, forexample, a first element, a first component or a first section discussedbelow could be termed a second element, a second component or a secondsection without departing from the teachings of the present disclosure.

Unless the context indicates otherwise, terms such as “same,” “equal,”“planar,” or “coplanar,” as used herein when referring to orientation,layout, location, shapes, sizes, amounts, or other measures do notnecessarily mean an exactly identical orientation, layout, location,shape, size, amount, or other measure, but are intended to encompassnearly identical orientation, layout, location, shapes, sizes, amounts,or other measures within acceptable variations that may occur, forexample, due to manufacturing processes. The term “substantially” may beused herein to reflect this meaning. For example, items described as“substantially the same,” “substantially equal,” or “substantiallyplanar,” may be exactly the same, equal, or planar, or may be the same,equal, or planar within acceptable variations that may occur, forexample, due to manufacturing processes.

In the present disclosure, a semiconductor device generally means adevice which can function by utilizing semiconductor characteristics,and an electro-optic device, a light-emitting display device, asemiconductor circuit, and an electronic device are all included in thecategory of the semiconductor device.

Note that, in the description of the present disclosure, above (or up)corresponds to the direction of the arrow of the direction Z, and below(or down) corresponds to the opposite direction of the arrow of thedirection Z.

FIG. 1 illustrates, in a flowchart diagram form, a method 10 forfabricating a semiconductor device in accordance with one embodiment ofthe present disclosure. FIGS. 2 and 3 illustrate, in schematiccross-sectional diagrams, part of a flow of fabricating a semiconductordevice in accordance with one embodiment of the present disclosure. FIG.4 illustrates, in a schematic top-view diagram, the semiconductor devicein accordance with FIG. 3.

In some embodiments, the method 10 comprises operations: S11, providinga substrate including a plurality of first regions and second regions;S13, forming a plurality of bit line contacts respectively over thefirst regions of the substrate; S15, forming a plurality of bit linesrespectively over the plurality of bit line contacts; S17, forming aplurality of capacitor contacts respectively over the second regions ofthe substrate; S19, forming a landing pad over one of the capacitorcontacts, wherein the landing pad comprises a protruding portion of acapacitor plug and a first spacer over the protruding portion, wherein awidth of the first spacer is larger than a width of the capacitor plug;S21, forming a conductive plug over the landing pad and in thedielectric layer, wherein the capacitor plug comprises a plurality ofnanowires, a conductive liner disposed over the nanowires, and aconductor disposed over the conductive liner; S23, forming a capacitorstructure over the conductive plug.

With reference to FIGS. 1 and 2, at step S11, a substrate 101 may beprovided, and a plurality of first regions and second regions are formedin the substrate 101. The substrate 101 may be formed of, for example,silicon, doped silicon, silicon germanium, silicon on insulator, siliconon sapphire, silicon germanium on insulator, silicon carbide, germanium,gallium arsenide, gallium phosphide, gallium arsenide phosphide, indiumphosphide, or indium gallium phosphide.

With reference to FIGS. 3 and 4, a plurality of isolation structures 103may be formed in the substrate 101. The plurality of isolationstructures 103 are separated from each other in a cross-sectional viewand define a plurality of active regions 105. The plurality of isolationstructures 103 may be formed of, for example, an insulating materialsuch as silicon oxide, silicon nitride, silicon oxynitride, siliconnitride oxide, fluoride-doped silicate, or the like. The plurality ofactive regions 105 may extend in a direction slanted with respect to adirection X in a top-view diagram. Note that, in the present disclosure,silicon oxynitride refers to a substance which contains silicon,nitrogen, and oxygen and in which a proportion of oxygen is greater thanthat of nitrogen. Silicon nitride oxide refers to a substance whichcontains silicon, oxygen, and nitrogen and in which a proportion ofnitrogen is greater than that of oxygen.

FIGS. 5 to 7 illustrate, in schematic cross-sectional diagrams, part ofthe flow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. FIG. 8 illustrates, in a schematictop-view diagram, the semiconductor device in accordance with FIG. 7.

With reference to FIG. 1 and FIGS. 5 to 8, a plurality of word lines 201may be formed in the substrate 101. In the embodiment depicted, theplurality of word lines 201 may extend along the direction X. Each oneof the plurality of word lines 201 includes a bottom layer 203, a middlelayer 205, a top layer 207, and a trench opening 209. With reference toFIG. 5, in the embodiment depicted, a photolithography process may beused to pattern the substrate 101 to define positions of a plurality oftrench openings 209. An etch process, such as an anisotropic dry etchprocess, may be performed to form the plurality of trench openings 209in the substrate 101. With reference to FIG. 6, after the etch process,the plurality of bottom layers 203 may be correspondingly formed andattached to sidewalls of the plurality of trench openings 209 andbottoms of the plurality of trench openings 209. The plurality of bottomlayers 203 may be formed of, for example, silicon oxide, siliconoxynitride, silicon nitride oxide, silicon nitride, or the like.

With reference to FIGS. 7 and 8, the plurality of middle layers 205 maybe correspondingly formed on the plurality of bottom layers 203. Topsurfaces of the plurality of middle layers 205 may be lower than a topsurface of the substrate 101. The plurality of middle layers 205 may beformed of, for example, doped polysilicon, metal material, or metalsilicide. Metal silicide may be, for example, nickel silicide, platinumsilicide, titanium silicide, molybdenum silicide, cobalt silicide,tantalum silicide, tungsten silicide, or the like. The plurality of toplayers 207 may be correspondingly formed on the plurality of middlelayers 205. Top surfaces of the plurality of top layers 207 may be atthe same vertical level as the top surface of the substrate 101. Theplurality of top layers 207 may be formed of, for example, siliconoxide, silicon oxynitride, silicon nitride oxide, silicon nitride, orthe like.

FIG. 9 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure.

With reference to FIG. 1 and FIG. 9, a plurality of first regions andsecond regions may be formed in the plurality of active regions 105 ofthe substrate 101. The plurality of doped regions may include a firstdoped region 301 and second doped regions 303. The first doped region301 is disposed between an adjacent pair of the plurality of word lines201. The second doped regions 303 are respectively disposed between theplurality of isolation structures 103 and the plurality of word lines201. The first doped region 301 and the second doped regions 303 arerespectively doped with a dopant such as phosphorus, arsenic, orantimony. The first doped region 301 and the second doped regionsrespectively have dopant concentrations ranging from about 1E17atoms/cm³ to about 1E19 atoms/cm³.

FIG. 10 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. FIG. 11 illustrates, in aschematic top-view diagram, the semiconductor device in accordance withFIG. 10.

With reference to FIG. 1 and FIGS. 10 and 11, at step S13, a pluralityof bit line contacts may be formed above the substrate. A firstinsulating film 801 may be formed on the substrate 101. The firstinsulating film 801 may be formed of, for example, silicon nitride,silicon oxide, silicon oxynitride, undoped silica glass, borosilicaglass, phosphosilica glass, borophosphosilica glass, or a combinationthereof, but is not limited thereto. The plurality of contacts 401 maybe formed in the first insulating film 801. A photolithography processmay be used to pattern the first insulating film 801 to define positionsof the plurality of contacts 401. An etch process, such as ananisotropic dry etch process, may be performed after thephotolithography process to form a plurality of openings in the firstinsulating film 801. After the etch process, a conductive material, forexample, aluminum, copper, tungsten, cobalt, or other suitable metal ormetal alloy is deposited, by a metallization process such as chemicalvapor deposition, physical vapor deposition, sputtering, or the like, inthe plurality of openings to form the plurality of contacts 401. Aplanarization process, such as chemical mechanical polishing, may beperformed after the metallization process to remove excess depositedmaterial and provide a substantially flat surface for subsequentprocessing steps.

In some embodiments, with reference to FIGS. 10 and 11, the contact 401is disposed on the first doped region 301 and is electrically connectedto the first doped region 301. In the embodiment depicted, the contact401 is formed including tungsten. Defects may be easily formed on a topsurface of the contact 401 formed including tungsten when the topsurface of the contact 401 is exposed to oxygen or air. The defects mayaffect the yield of the semiconductor device.

FIG. 12 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. FIG. 13 illustrates, in aschematic top-view diagram, the semiconductor device in accordance withFIG. 12.

With reference to FIG. 1 and FIGS. 12 and 13, a plurality of bit linecontacts 405 may be formed above the substrate 101. (Only one bit linecontact 405 is shown in FIG. 12.) A second insulating film 803 may beformed on the first insulating film 801. The second insulating film 803may be formed of a same material as the material of the first insulatingfilm 801, but is not limited thereto. A photolithography process may beused to pattern the second insulating film 803 to define positions ofthe plurality of bit line contacts 405. An etch process, such as ananisotropic dry etch process, may be performed after thephotolithography process to form a plurality of bit line contactopenings in the second insulating film 803. A top surface of the contact401 may be exposed through the plurality of bit line contact openings. Acleaning process using a reducing agent may be optionally performed toremove the defects on the top surface of the contact 401 formedincluding tungsten. The reducing agent may be titanium tetrachloride,tantalum tetrachloride, or a combination thereof.

With reference to FIGS. 12 and 13, after the cleaning process, a firstcoverage layer 407 including tungsten nitride may be formed to coverbottoms and sidewalls of the plurality of bit line contact openings. Thefirst coverage layer 407 may prevent the top surface of the contact 401formed including tungsten from being exposed to oxygen or air;therefore, the first coverage layer 407 may reduce formation of thedefects on the top surface of the contact 401 formed including tungsten.A conductive material, for example, aluminum, copper, tungsten, cobalt,or other suitable metal or metal alloy is deposited, by a metallizationprocess such as chemical vapor deposition, physical vapor deposition,sputtering, or the like, in the plurality of bit line contact openingsto form the plurality of bit line contacts 405. A planarization process,such as chemical mechanical polishing, may be performed after themetallization process to remove excess deposited material and provide asubstantially flat surface for subsequent processing steps.

With reference to FIGS. 12 and 13, the plurality of bit line contacts405 are correspondingly electrically connected to the first contacts401; that is to say, the plurality of bit line contacts 405 areelectrically coupled to the first doped region 301.

FIG. 14 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. FIG. 15 illustrates, in aschematic top-view diagram, the semiconductor device in accordance withFIG. 14.

With reference to FIG. 1 and FIGS. 14 and 15, at step S15, a pluralityof bit lines may be formed respectively over the plurality of bit linecontact on the substrate. (Only one bit line 409 is shown in FIG. 14.) Athird insulating film 805 may be formed on the second insulating film803. The third insulating film 805 may be formed of a same material asthe material of the first insulating film 801, but is not limitedthereto. A photolithography process may be used to pattern the thirdinsulating film 805 to define positions of the plurality of bit lines409. An etch process, such as an anisotropic dry etch process, may beperformed after the photolithography process to form a plurality of bitline trench openings 408 in the third insulating film 805. In someembodiments, the photolithography process may also pattern the thirdinsulating film 805 to define positions of a plurality of contact holes402, and an etch process may be performed to form a plurality of contactholes 402 penetrating through the third insulating film 805, the secondinsulating film 803, and the first insulating film 801. In other words,the contact holes 402 are considered deep holes, while the bit linetrench openings 408 are considered relatively shallow holes.

FIG. 16 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. FIG. 17 illustrates, in aschematic top-view diagram, the semiconductor device in accordance withFIG. 16. In some embodiments, the bit line trench openings 408 and thecontact holes 402 may be filled with material by processes such aschemical vapor deposition, physical vapor deposition, sputtering, or thelike. In some embodiments, the contact holes 402 is deeper than the bitline trench openings 408, and the bit line trench openings 408 may becompletely filled by a filling material 408-1, and the contact holes 402may be partially filled by a filling material 402-1, which can be thesame as the filling material 408-1. In some embodiments, the upperportion of the contact holes 402 in the third insulating film 805 is notfilled by the filling material 402-1.

With reference to FIG. 1 and FIGS. 18 and 21, at step S17, a pluralityof capacitor contacts respectively over the second regions of thesubstrate. FIG. 18 illustrates, in a schematic cross-sectional diagram,part of the flow of fabricating the semiconductor device in accordancewith one embodiment of the present disclosure. FIG. 19 illustrates, in aschematic top-view diagram, the semiconductor device in accordance withFIG. 18. In some embodiments, an etch process, such as an isotropic etchprocess, may be performed to remove a portion of the third insulatingfilm 805 around the contact holes 402 to form a plurality of transformedholes 404 having a narrow portion 404-1 occupied by the filling material402-1 in the second insulating film 803 and a wide portion 404-2 in thethird insulating film 805.

FIG. 20 illustrates, in a schematic cross-sectional diagram, part of theflow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. FIG. 21 illustrates, in aschematic top-view diagram, the semiconductor device in accordance withFIG. 20. In some embodiments, the filling material 402-1 and the fillingmaterial 408-1 are stripped from the transformed holes 404 and the bitline trench openings 408, respectively. After stripping the fillingmaterial, a conductive material, for example, aluminum, copper,tungsten, cobalt, or other suitable metal or metal alloy is deposited,by a metallization process such as chemical vapor deposition, physicalvapor deposition, sputtering, or the like, in the plurality of bit linetrench openings 408 to form a plurality of bit lines 409 and in thetransformed holes 404 to form a plurality of capacitor contacts 403. Aplanarization process, such as chemical mechanical polishing, may beperformed after the metallization process to remove excess depositedmaterial and provide a substantially flat surface for subsequentprocessing steps.

In some embodiments, the capacitor contact 403 includes a neck portion403-1 and a head portion 403-2 over the neck portion 403-1, wherein anupper width W1 of the head portion 403-2 is larger than an upper widthW2 of the neck portion 403-1. In some embodiments, the upper width W2 ofthe neck portion 403-1 is substantially the same as a bottom width ofthe head portion 403-2. In some embodiments, the head portion 403-2 hasa curved sidewall 403-3. In some embodiments, the head portion hastapered profile.

With reference to FIGS. 20 and 21, the plurality of bit lines 409 mayextend along a direction Y and implemented as wavy lines in a top-viewdiagram. The plurality of bit line contacts 405 are located atintersections of the plurality of bit lines 409 and the plurality ofactive regions 105. The plurality of bit lines 409 implemented as wavylines may increase a contact area between the plurality of bit linecontacts 405 and the plurality of active regions 105; therefore, acontact resistance between the plurality of bit line contacts 405 andthe plurality of active regions 105 may be reduced.

With reference to FIG. 1 and FIG. 22, at step S19, a plurality ofcapacitor plugs are respectively formed over the plurality of capacitorcontacts. FIG. 22 illustrates, in a schematic cross-sectional diagram,part of the flow of fabricating the semiconductor device in accordancewith one embodiment of the present disclosure. With reference to FIG. 1and FIG. 22, a plurality of capacitor plugs 411 may be formed above thesubstrate 101. A fourth insulating film 807 may be formed on the thirdinsulating film 805. The fourth insulating film 807 may be formed of asame material as the material of the first insulating film 801, but isnot limited thereto. A photolithography process may be used to patternthe fourth insulating film 807 to define positions of the plurality ofcapacitor plugs 411. An etch process, such as an anisotropic dry etchprocess, may be performed after the photolithography process to form aplurality of plug openings passing through the fourth insulating film807, the third insulating film 805, and the second insulating film 803.After the etch process, a conductive material, for example, aluminum,copper, tungsten, cobalt, or other suitable metal or metal alloy isdeposited, by a metallization process such as chemical vapor deposition,physical vapor deposition, sputtering, or the like, in the plurality ofplug openings to form the plurality of capacitor plugs 411 over the headportion 403-2. A planarization process, such as chemical mechanicalpolishing, may be performed after the metallization process to removeexcess deposited material and provide a substantially flat surface forsubsequent processing steps. In some embodiments, the capacitor plug 411comprises a doped polysilicon layer 412A, and a cobalt silicide layer412B disposed over the doped polysilicon layer 412A.

With reference to FIG. 1 and FIGS. 23 to 26, at step S21, a plurality offirst spacers are respectively formed over a plurality of protrudingportions of the plurality of capacitor plugs. FIG. 23, illustrates, in aschematic cross-sectional diagram, part of the flow of fabricating thesemiconductor device in accordance with one embodiment of the presentdisclosure. With reference to FIG. 1 and FIG. 23, an etching backprocess is performed to remove a top portion of the fourth insulatingfilm 807 to expose a protruding portion 411A of the capacitor plug 411.In some embodiments, after the etching back process, the top surface ofthe capacitor plug 411 is higher than that of the fourth insulating film807, and the sidewall of the capacitor plug 411 (protruding portion411A) is exposed.

FIG. 24, illustrates, in a schematic cross-sectional diagram, part ofthe flow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. In some embodiments, a depositionprocess is performed to form a liner layer 808, covering the top surfaceof the fourth insulating film 807, the top surface of the protrudingportion 411A, and the sidewall of the protruding portion 411A.

FIG. 25, illustrates, in a schematic cross-sectional diagram, part ofthe flow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. In some embodiments, ananisotropic dry etching process is performed to remove a portion of theliner layer 808 so as to form a plurality of first spacers 808Arespectively on the protruding portion 411A. In some embodiments, thefirst spacer 808A comprises metal silicide and is disposed on a sidewallof the protruding portion 411A. In some embodiments, the width W4 of thefirst spacer 808A is larger than the width W3 of the capacitor plug 411.

FIG. 26, illustrates, in a schematic cross-sectional diagram, part ofthe flow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure. In some embodiments, asilicidation (SALICIDE) process is performed to form a plurality ofsecond spacers 808B respectively over the first spacers 808A. In someembodiments, the first spacer 808A comprises polysilicon and is disposedon a sidewall of the protruding portion 411A, and the second spacer 808Bcomprises metal silicide from the polysilicon of the first spacer 808A.In some embodiments, the protruding portion 411A, the first spacer 808A,and the second spacer 808B form a landing pad 810 over the capacitorcontact 403.

FIG. 27, illustrates, in a schematic cross-sectional diagram, part ofthe flow of fabricating the semiconductor device in accordance with oneembodiment of the present disclosure, and FIGS. 28 to 33 illustrates, ina close-up schematic cross-sectional diagram, part of the flow offabricating the conductive plug in accordance with one embodiment of thepresent disclosure. In some embodiments, a fifth insulating film 814having a conductive plug 816 may be formed over the landing pad 810. Thefifth insulating film 814 may be formed of a same material as thematerial of the first insulating film 801, but is not limited thereto.

With reference to FIG. 28, in some embodiments, openings 816-1, one ofwhich is shown in FIGS. 28 to 33, are formed in the fifth insulatingfilm 814 by conventional lithography and etching, exposing a portion ofthe landing pad 810. The location of the openings 816-1 defines theregion that will be occupied by the conductive plug 816.

With reference to FIG. 29, in some embodiments, catalyst dots 816-2 suchas Au, Ga, Al, Ti, and Ni for the nanowire growth are formed over theexposed landing pad 810. The catalyst dots 816-2 can be formed bypatterning a catalyst film into dots or by dispensing a colloidcontaining said catalyst. It is noted that the size, e.g., width, of thecatalyst dots 816-2 defines the nanowire diameter. Thus, accuratecontrol of the dot size is important for obtaining a tight distributionof the nanowire's diameter. Other methods for introducing the catalystare also possible. For example, a thin catalyst film will agglomerateinto separated catalyst droplets if annealed at elevated temperatures(e.g., above 350° C.). The catalyst agglomeration method, however, doesnot yield a narrow distribution of the dot size as typically obtained bythe catalyst suspension method. Moreover, the catalyst dots can beformed utilizing a self-assembly process. The term “self-assembly” isused herein to denote the spontaneous organization of a material into aregular pattern.

With reference to FIG. 30, in some embodiments, nanowires 816-3 aregrown from the catalyst dots 816-2 and perpendicular to the exposedsurface of the landing pad 810 in the opening 816-1. The growth of thenanowires 816-3 is assisted by the catalyst dots 816-2 and is typicallycarried out by chemical vapor deposition (CVD) or plasma enhancedchemical vapor deposition (PECVD). The growth temperature depends on theprecursor used. For example, for silane (SiH4) a typical growthtemperature is from about 370° C. to about 500° C. For silicontetrachloride (SiCl4), the growth temperature is from about 800° C. toabout 950° C. By adding chlorine to SiH4, the growth temperature can beraised to above 600° C. The growth rate of the nanowires 816-3 dependson the growth temperature and the gas pressure in the growth chamber.For example, a typical CVD growth rate for SiH4 diluted with H2 (1:1) ata pressure of 1 torr and a growth temperature of 450° C. is about 7.6μm/hour. The anisotropic growth of the nanowires 816-3 is described bythe vapor-liquid-solid (VLS) mechanism. Note that the nanowires 816-3can be comprised of the same or different material as that of thesemiconductor substrate. In one embodiment, the nanowires 816-3 bycomprised of a material that is different from the semiconductorsubstrate. In yet another embodiment, the nanowires are single-crystalSi nanowires having substantially the same crystal orientation. In thespecific example described herein in which Si nanowires are formed on a(111) oriented Si substrate, the silicon nanowires orientation is (111)as it is seeded from the substrate which also has the (111) orientation.The nanowires 816-3 are grown to a length that typically exceeds thethickness of the fifth insulating film 814.

With reference to FIG. 31, in some embodiments, a conformal silicidelayer 816-4 is blanket deposited over the landing pad 810 and thenanowires 816-3. Some examples of silicide layer include, but are notlimited to, cobalt silicide. The deposition of the cobalt silicide layer816-4 is performed by techniques such as, for example, CVD or atomiclayer deposition (ALD).

With reference to FIG. 32, in some embodiments, a conformal conductor816-5 is deposited over the silicide layer 816-4. The conductor 816-5fills the space between the nanowires 816-3. The conductor 816-5 can bedoped polysilicon, or a conductive metal such as tungsten (W), aluminum(Al), copper (Cu), or tantalum (Ta). Alloys of the conductive metals aswell as silicides or nitrides of said conductive metals are alsocontemplated herein.

With reference to FIG. 33, in some embodiments, the structure in FIG. 32is then planarized by CMP. The fifth insulating film 814 is used as aCMP stop layer. The CMP step trims the nanowires 816-3 to be all of thesame length. In some embodiments, the tip of each nanowire 816-3 issilicided, using the SALICIDE process. Subsequently, a conductor 816-7is formed over the nanowires 816-3, the silicide layer 816-4, and theconductor 816-5.

With reference to FIG. 1 and FIGS. 34 to 36, at step S23, a plurality ofcapacitor structures are formed respectively over the plurality of firstspacers of the landing pads via the plurality of conductive plugs 816.FIGS. 34 to 36 illustrate, in schematic cross-sectional diagrams, partof the flow of fabricating the semiconductor device in accordance withone embodiment of the present disclosure.

In some embodiments, the plurality of capacitor structures 501 mayinclude a bottom electrode 505, a capacitor insulating layer 507, and atop electrode 509. With reference to FIG. 34, a fifth insulating film809 may be formed on the fourth insulating film 807. The fifthinsulating film 809 may be formed of a same material as the material ofthe first insulating film 801, but is not limited thereto. Aphotolithography process may be used to pattern the fifth insulatingfilm 809 to define positions of a plurality of capacitor trenches 503.An etch process, such as an anisotropic dry etch process, may beperformed after the photolithography process to form the plurality ofcapacitor trenches 503 passing through the fifth insulating film 809.The plurality of plugs 816 may be exposed through the plurality ofcapacitor trenches 503.

With reference to FIG. 35, a plurality of bottom electrodes 505 may becorrespondingly respectively formed in the plurality of capacitortrenches 503, in other words, the plurality of bottom electrodes 505 maybe inwardly formed in the fifth insulating film 809. The plurality ofbottom electrodes 505 may be formed of, for example, doped polysilicon,metal silicide, aluminum, copper, or tungsten. The plurality of bottomelectrodes 505 may be respectively correspondingly connected to theplurality of plugs 816.

With reference to FIG. 35, the capacitor insulating layer 507 may beformed to attach to sidewalls and bottoms of the plurality of bottomelectrodes 505 and the top surfaces of the fifth insulating film 809.The capacitor insulating layer 507 may be a single layer or multiplelayers. In the embodiment depicted, the capacitor insulating layer 507may be a single layer or multiple layers. Specifically, the capacitorinsulating layer 507 may be a single layer formed of a high dielectricconstant material such as barium strontium titanate, lead zirconiumtitanate, titanium oxide, aluminum oxide, hafnium oxide, yttrium oxide,zirconium oxide, or the like. Alternatively, in another embodiment, thecapacitor insulating layer 507 may be multiple layers consisting ofsilicon oxide, silicon nitride, and silicon oxide.

With reference to FIGS. 36 and 37, the top electrode 509 may be formedto fill the plurality of capacitor trenches 503 and cover the capacitorinsulating layer 507. The top electrode 509 may be formed of, forexample, doped polysilicon, copper, or aluminum.

FIGS. 38 to 41 illustrate, in schematic cross-sectional diagrams, partof the flow of fabricating the semiconductor device in accordance withone embodiment of the present disclosure. In some embodiments, a bottomvia 413 and a first conductive layer 415 may be formed above thesubstrate 101. With reference to FIG. 38, a sixth insulating film 811may be formed on the fifth insulating film 809. The sixth insulatingfilm 811 may be formed of a same material as the material of the firstinsulating film 801, but is not limited thereto. A photolithographyprocess may be used to pattern the sixth insulating film 811 to definepositions of the bottom via 413. An etch process, such as an anisotropicdry etch process, may be performed after the photolithography process toform a bottom via opening passing through the sixth insulating film 811.After the etch process, a conductive material, for example, aluminum,copper, tungsten, cobalt, or other suitable metal or metal alloy isdeposited, by a metallization process such as chemical vapor deposition,physical vapor deposition, sputtering, or the like, in the bottom viaopening to form the bottom via 413 in the sixth insulating film 811. Aplanarization process, such as chemical mechanical polishing, may beperformed after the metallization process to remove excess depositedmaterial and provide a substantially flat surface for subsequentprocessing steps.

With reference to FIG. 38, in the embodiment depicted, the bottom via413 is formed including tungsten. Defects may be easily formed on a topsurface of the bottom via 413 formed including tungsten when the topsurface of the bottom via 413 is exposed to oxygen or air. The defectsmay affect the yield of the semiconductor device.

With reference to FIG. 39, a seventh insulating film 813 may be formedon the sixth insulating film 811. The seventh insulating film 813 may beformed of a same material as the material of the first insulating film801, but is not limited thereto. A photolithography process may be usedto pattern the seventh insulating film 813 to define a position of thefirst conductive layer 415. An etch process, such as an anisotropic dryetch process, may be performed after the photolithography process toform a first conductive layer trench in the seventh insulating film 813.The top surface of the bottom via 413 may be exposed through the firstconductive layer trench. A cleaning process using a reducing agent maybe optionally performed to remove the defects on the top surface of thebottom via 413 formed including tungsten. The reducing agent may betitanium tetrachloride, tantalum tetrachloride, or combination thereof.

With reference to FIGS. 39 and 40, after the cleaning process, a secondcoverage layer 417 formed including tungsten nitride may be formed tocover a bottom and sidewalls of the first conductive layer trench. Thesecond coverage layer 417 may prevent the top surface of the bottom via413 formed including tungsten from being exposed to oxygen or air;therefore, the second coverage layer 417 may reduce formation of thedefects on the top surface of the bottom via 413 formed includingtungsten. A conductive material, for example, aluminum, copper,tungsten, cobalt, or other suitable metal or metal alloy is deposited,by a metallization process such as chemical vapor deposition, physicalvapor deposition, sputtering, or the like, in the first conductive layertrench to form the first conductive layer 415. A planarization process,such as chemical mechanical polishing, may be performed after themetallization process to remove excess deposited material and provide asubstantially flat surface for subsequent processing steps.

FIG. 41 illustrates, in a schematic cross-sectional view diagram, asemiconductor device in accordance with one embodiment of the presentdisclosure.

With reference to FIG. 41, a semiconductor device may include asubstrate 101, a plurality of isolation structures 103, a plurality ofword lines 201, a plurality of doped regions, a plurality of insulatingfilms, a plurality of contacts, a plurality of bit line contacts 405, afirst coverage layer 407, a plurality of bit lines 409, a plurality ofplugs 411, a plurality of landing pads 810, a plurality of plugs 816, abottom via 413, a first conductive layer 415, a second coverage layer417, and a plurality of capacitor structures 501.

With reference to FIG. 41, the plurality of isolation structures 103 maybe disposed in the substrate 101 and separated from each other. Theplurality of isolation structures 103 may define a plurality of activeregions 105. The plurality of word lines 201 may be disposed in thesubstrate 101 and separated from each other. Each one of the pluralityof word lines 201 includes a bottom layer 203, a middle layer 205, and atop layer 207. The plurality of bottom layers 203 may be respectivelyinwardly disposed in the substrate 101. The plurality of middle layers205 may be respectively correspondingly disposed on the plurality ofbottom layers 203. Top surfaces of the plurality of middle layers 205may be lower than a top surface of the substrate 101. The plurality oftop layers 207 may be respectively correspondingly disposed on theplurality of middle layers 205. Top surfaces of the plurality of toplayers 207 may be at the same vertical level as the top surface of thesubstrate 101.

With reference to FIG. 41, a plurality of doped regions may be disposedin the plurality of active regions 105 of the substrate 101. Each of theplurality of doped regions includes a first doped region 421 and seconddoped regions 423. For each of the plurality of doped regions, the firstdoped region 421 is disposed between an adjacent pair of the pluralityof word lines 201. The second doped regions 423 are respectivelydisposed between the plurality of isolation structures 103 and theplurality of word lines 201.

With reference to FIG. 41, the plurality of insulating films may bedisposed above the substrate 101. The plurality of insulating films mayinclude a first insulating film 801, a second insulating film 803, athird insulating film 805, a fourth insulating film 807, a fifthinsulating film 809, a sixth insulating film 811, and a seventhinsulating film 813. The first insulating film 801 may be disposed onthe substrate 101. The plurality of contacts may be disposed in thefirst insulating film 801. The plurality of contacts may include acontact 401 and capacitor contacts 403. The contact 401 is disposed onthe first doped region 421 and is electrically connected to the firstdoped region 421. The capacitor contacts 403 are respectively disposedon the second doped regions 423 and are respectively electricallyconnected to the second doped regions 423. In the embodiment depicted,the contact 401 is formed including tungsten.

With reference to FIG. 41, the second insulating film 803 may bedisposed on the first insulating film 801. The plurality of bit linecontacts 405 may be disposed in the second insulating film 803. (Onlybit line contact is shown in FIG. 41.) The first coverage layer 407 maybe disposed in the second insulating film 803 and on a top surface ofthe contact 401; in other words, the first coverage layer 407 may bedisposed between the plurality of bit line contacts 405 and the contact401. In addition, the first coverage layer 407 may be disposed on andattached to sidewalls of the plurality of bit line contacts 405. Thefirst coverage layer 407 may include tungsten nitride.

With reference to FIG. 41, the third insulating film 805 may be disposedon the second insulating film 803. The plurality of bit lines 409 may bedisposed in the third insulating film 805 and on the plurality of bitline contacts 405 and the first coverage layer 407. (Only one bit line409 is shown in FIG. 41.) The fourth insulating film 807 may be disposedon the third insulating film 805. The plurality of plugs 411 may bedisposed to pass through the fourth insulating film 807, the thirdinsulating film 805, and the second insulating film 803. The pluralityof plugs 411 may be respectively correspondingly electrically connectedto the capacitor contacts 403.

With reference to FIG. 41, the capacitor contact 403 includes a neckportion 403-1 and a head portion 403-2 over the neck portion 403-1,wherein an upper width W1 of the head portion 403-2 is larger than anupper width W2 of the neck portion 403-1. In some embodiments, the upperwidth W2 of the neck portion 403-1 is substantially the same as a bottomwidth of the head portion 403-2. In some embodiments, the head portion403-2 has a curved sidewall 403-3. In some embodiments, the head portionhas tapered profile.

With reference to FIG. 41, in some embodiments, a plurality of firstspacers 808A are respectively disposed on the protruding portion 411A ofthe plugs 411. In some embodiments, the first spacer 808A comprisesmetal silicide and is disposed on a sidewall of the protruding portion411A. In some embodiments, the width W4 of the first spacer 808A islarger than the width W3 of the capacitor plug 411. In some embodiments,a plurality of second spacers 808B are respectively disposed over thefirst spacers 808A. In some embodiments, the first spacer 808A comprisespolysilicon and is disposed on a sidewall of the protruding portion411A, and the second spacer 808B comprises metal silicide from thepolysilicon of the first spacer 808A. In some embodiments, theprotruding portion 411A, the first spacer 808A, and the second spacer808B form a landing pad 810 over the capacitor contact 403.

With reference to FIG. 41, the fifth insulating film 809 may be disposedon the fourth insulating film 807. The plurality of capacitor structures501 may be disposed in the fifth insulating film 809. The plurality ofcapacitor structures 501 may include a plurality of bottom electrodes505, a capacitor insulating layer 507, and a top electrode 509. Theplurality of bottom electrodes 505 may be inwardly disposed in the fifthinsulating film 809 and respectively correspondingly electricallyconnected to the plurality of plugs 816. The capacitor insulating layer507 may be disposed on the plurality of bottom electrodes 505. The topelectrode 509 may be disposed on the capacitor insulating layer 507.

With reference to FIG. 41, the sixth insulating film 811 may be disposedon the fifth insulating film 809. The bottom via 413 may be disposed inthe sixth insulating film 811 and electrically connected to the topelectrode 509. The bottom via 413 may include tungsten. A seventhinsulating film 813 may be disposed on the sixth insulating film 811.The first conductive layer 415 may be disposed in the seventh insulatingfilm 813 and above the bottom via 413. The second coverage layer 417 maybe disposed on a top surface of the bottom via 413, and the secondcoverage layer 417 may be disposed between the bottom via 413 and thefirst conductive layer 415. In addition, the second coverage layer 417may be disposed on and attached to sidewalls of the first conductivelayer 415. The second coverage layer 417 may include tungsten nitride.

FIGS. 42 and 43 illustrate, in schematic cross-sectional view diagrams,some semiconductor devices in accordance with some embodiments of thepresent disclosure.

With reference to FIG. 42, the semiconductor device may include aplurality of third coverage layers 419. The plurality of third coveragelayers 419 may be respectively correspondingly disposed between thecapacitor contacts 403 and the plurality of plugs 411. In other words,the plurality of third coverage layers 419 may be respectivelycorrespondingly disposed on top surfaces of the capacitor contacts 403formed including tungsten. The plurality of third coverage layers 419may be respectively correspondingly disposed on and attached tosidewalls of the plurality of plugs 411. The plurality of third coveragelayers 419 may include tungsten nitride. In the present embodiment, onlythe first coverage layer 407, the second coverage layer 417, and theplurality of third coverage layers 419 are disposed on the contact 401,the bottom via 413, and the capacitor contacts 403, respectively;however, other conductive layers or vias may also applicable.

Note that, in the present embodiment, a coverage layer may be regardedas the first coverage layer 407, the second coverage layer 417, or thethird coverage layer 419, but is not limited thereto. A conductivefeature may be regarded as the contact 401, the second contact 403, orthe bottom via 413, but is not limited thereto.

With reference to FIG. 43, the semiconductor device may include a firstbarrier layer 421. The first barrier layer 421 may be disposed betweenthe first coverage layer 407 and the plurality of bit line contacts 405.The first barrier layer 421 may be formed of, for example, titanium,titanium nitride, titanium-tungsten alloy, tantalum, tantalum nitride,or the combination thereof. The first barrier layer 421 may improveadhesion between the first coverage layer 407 and the plurality of bitline contacts 405.

One aspect of the present disclosure provides a semiconductor device,comprising: a substrate having a plurality of first regions and secondregions; a plurality of bit line contacts and a plurality of capacitorcontacts disposed respectively over the plurality of first regions andsecond regions; a landing pad disposed over one of the plurality ofcapacitor contacts, the landing pad comprising a protruding portion of acapacitor plug and a first spacer disposed on a sidewall of theprotruding portion; a conductive plug disposed over the landing pad,wherein the capacitor plug comprises a plurality of nanowires, aconductive liner disposed over the plurality of nanowires, and aconductor disposed over the conductive liner; a plurality of bit linesdisposed respectively over the plurality of bit line contacts; and acapacitor structure disposed over the conductive plug.

Another aspect of the present disclosure provides a method forfabricating a semiconductor device, comprising: providing a substrateincluding a plurality of first regions and second regions; forming aplurality of bit line contacts respectively over the plurality of firstregions; forming a plurality of bit lines respectively over theplurality of bit line contacts; forming a plurality of capacitorcontacts respectively over the plurality of second regions; forming alanding pad over one of the plurality of capacitor contacts, wherein thelanding pad comprises a protruding portion of a capacitor plug and afirst spacer on a sidewall of the protruding portion; forming aconductive plug over the landing pad, wherein the capacitor plugcomprises a plurality of nanowires, a conductive liner over theplurality of nanowires, and a conductor over the conductive liner; andforming a capacitor structure over the conductive plug; wherein at leastone of the plurality of bit lines is a wavy line extending between twoadjacent capacitor contacts.

High aspect ratio conductive plug is implemented by the nanowires toelectrically connect the source/drain regions in the substrate and thecapacitor structures over the source/drain regions.

Furthermore, the landing pad has the first spacer, wherein a width ofthe first spacer is larger than a width of the capacitor plug, themisalignment between the subsequently formed capacitor structure and thelanding pad can be dramatically solved, wherein a width of the firstspacer is larger than a width of the capacitor plug.

In addition, due to the capacitor contact having the neck portion andthe head portion with a tapered profile, the misalignment between thesubsequently formed capacitor structure and the capacitor contact can bedramatically solved. In addition, the coverage layer may reduceformation of defects in the semiconductor device; therefore, the yieldof the semiconductor device increases correspondingly.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims. For example,many of the processes discussed above can be implemented in differentmethodologies and replaced by other processes, or a combination thereof.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the present disclosure, processes, machines,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed, that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized according to the presentdisclosure. Accordingly, the appended claims are intended to includewithin their scope such processes, machines, manufacture, compositionsof matter, means, methods, and steps.

What is claimed is:
 1. A semiconductor device, comprising: a substratehaving a plurality of first regions and second regions; a plurality ofbit line contacts and a plurality of capacitor contacts disposedrespectively over the plurality of first regions and second regions; aplurality of landing pads disposed respectively over the plurality ofcapacitor contacts, at least one of the plurality of landing padscomprising a protruding portion of a capacitor plug and a first spacerdisposed on a sidewall of the protruding portion; a plurality ofconductive plugs disposed respectively over the plurality of landingpads, wherein the plurality of capacitor plugs comprise a plurality ofnanowires, a conductive liner disposed over the plurality of nanowires,and a conductor disposed over the conductive liner; a plurality of bitlines disposed respectively over the plurality of bit line contacts; anda capacitor structure disposed over the conductive plug.
 2. Thesemiconductor device of claim 1, wherein the first spacer comprisesmetal silicide, and a width of the first spacer is larger than a widthof the capacitor plug.
 3. The semiconductor device of claim 1, whereinat least one of the plurality of bit lines is a wavy line extendingbetween two adjacent capacitor contacts.
 4. The semiconductor device ofclaim 1, further comprising a second spacer disposed over the firstspacer, wherein the first spacer comprises polysilicon.
 5. Thesemiconductor device of claim 4, wherein the second spacer comprisesmetal silicide.
 6. The semiconductor device of claim 1, wherein at leastone of the plurality of capacitor contacts having a neck portion and ahead portion over the neck portion.
 7. The semiconductor device of claim6, wherein the upper width of the head portion is larger than a bottomwidth of the head portion, and the head portion has a curved sidewall.8. The semiconductor device of claim 6, wherein the upper width of theneck portion is substantially the same as a bottom width of the headportion.
 9. The semiconductor device of claim 6, wherein the headportion has tapered profile.
 10. The semiconductor device of claim 6,wherein an upper width of the head portion is larger than an upper widthof the neck portion.
 11. A method for fabricating a semiconductordevice, comprising: providing a substrate including a plurality of firstregions and second regions; forming a plurality of bit line contactsrespectively over the plurality of first regions; forming a plurality ofbit lines respectively over the plurality of bit line contacts; forminga plurality of capacitor contacts respectively over the plurality ofsecond regions; forming a plurality of landing pads respectively overthe plurality of capacitor contacts, wherein at least one of theplurality of landing pads comprises a protruding portion of a capacitorplug and a first spacer on a sidewall of the protruding portion; forminga plurality of conductive plugs respectively over the plurality oflanding pads, wherein the plurality of capacitor plugs comprise aplurality of nanowires, a conductive liner over the plurality ofnanowires, and a conductor over the conductive liner; and forming acapacitor structure over the conductive plug; wherein at least one ofthe plurality of bit lines is a wavy line extending between two adjacentcapacitor contacts.
 12. The method for fabricating a semiconductordevice of claim 11, wherein forming a conductive plug comprises: forminga plurality of catalyst dots over the landing pad; forming the pluralityof nanowires from the plurality of catalyst dots; depositing a silicidelayer and a conductor over the plurality of nanowires; and planarizingthe plurality of nanowires to trim the plurality of nanowires to be ofsame length.
 13. The method for fabricating a semiconductor device ofclaim 11, wherein the first spacer comprises metal silicide.
 14. Themethod for fabricating a semiconductor device of claim 11, furthercomprising: forming a plurality of second spacers respectively over theplurality of first spacers, wherein the first spacer comprisespolysilicon.
 15. The method for fabricating a semiconductor device ofclaim 14, wherein the second spacer comprises metal silicide.
 16. Themethod for fabricating a semiconductor device of claim 11, wherein atleast one of the plurality of capacitor contacts having a neck portionand a head portion over the neck portion, wherein an upper width of thehead portion is larger than an upper width of the neck portion.
 17. Themethod for fabricating the semiconductor device of claim 16, whereinforming a plurality of capacitor contacts comprise: forming a contacthole in a dielectric stack having a first layer and a second layer overthe first layer; removing a portion of the second layer around thecontact hole to form a transformed hole having a narrow portion in thefirst layer and a wide portion in the second layer; and filling aconductive material into the transformed hole.
 18. The method forfabricating the semiconductor device of claim 17, wherein the contacthole is formed integrally with a bit line trench in the second layer.19. The method for fabricating the semiconductor device of claim 18,further comprising: filling the bit line trench and a lower portion ofthe contact hole with a filling material.
 20. The method for fabricatingthe semiconductor device of claim 11, wherein a width of the firstspacer is larger than a width of the capacitor plug.